Electric thermometer



(No Model.) 2Sheets S heet 1.

M. A. AGELASTO.

ELECTRIC THBRMOM'ETER. No. 571,426. Patented Nov. 17, 1896.

THE NOFIRXS PETERS no, wow-urns" YVASHYNGTUN, a. c.

(No Model.)

I 2 Sheets-Sheet 2. M. A. AGELASTO. ELECTRIC THERMOMETER.

No. 571,426. Patented Nov. 1'7, 1896.

NITED STATES PATENT FFICE.

MICHAEL ALEXANDER AGELASTO, OF NORFOLK, VIRGINIA.

ELECTRIC T;HERMOMETER.

SPECIFICATION forming part of Letters Patent No. 571,426, dated November17, 1896.

Application filed May 8, 1896. Serial No. 590,722. (No model.)

To all whom it may concern.-

Be it known that I, MIcHAEL ALEXANDER AGELASTO, a citizenof the UnitedStates, re-

siding at Norfolk, in the county of Norfolk and State of Virginia, haveinvented a new and usefulElectric Thermometer, of which the following isa specification.

This invention relates to electric thermometers or thermo-indicators,and it has for its object to provide a simple and practical instrumentof this character especially de-. signed for use 1n hospitals, privateresidences,

hotels, cold-storage warehouses, and the like. To this end the main andprimary object of the present invention is to provide a new and usefulconstruction of electric thermometer for determining at any desiredplace the exact variation of temperature existing at another place orplaces, and this result is primarily accomplished by the directinfluence of heat on the electrical resistance of a coil of fine wireand by the indicating or register ing of the variation of current due tothe variation of resistance in the thermostatic coil of the instrumentby changes in temperature.

With these and other objects in view, which will readily appear as thenature of the in vention is better understood, the same consists in thenovel construction, combination, and arrangement of parts hereinaftermore fully described, illustrated, and claimed.

In the drawings, Figure 1 is a front elevation of an electricthermometer constructed in accordance with this invention. Fig. 2 is anenlarged perspective View of the instrument, the casing beingillustrated as broken away. Fig. 3 is a sectional view on the line 3 3of Fig. 1. Fig. 4 is a detail sectional view illustrating the pivotalsupport of the mov able dead-beat helix 011 top of the stationarymetallic core. y

Referring to the accompanying drawings, the numeral 1 designates asuitable case or box provided with an enlarged upper portion 2 and atthe top with a bracket extension 3, which bracket extension provides aconvenient support for the instrument, whereby the same can be readilyhung on a wall or the like. The enlarged upper portion 2 of the case orbox 1 is open at its front side and has fitted therein the curved glassfront 4;, in rear of which, within the box, is arranged the metalliccore 8. The stationary metallic core 8 is preferably of a cylindricalshape and is made of iron, and the said stationary metallic core 8 isprovided at one side with a supporting-screw 9, adapted to be fitted inthe rear side of the case or box 1 to provide for properly supportingthe core in a position between the two opposite poles of the permanentmagnet 6.

The stationary metallic cylindrical core 8 has projected from the topside thereof a short pivot-pin 10, on which loosely turns a bearing cupor socket 11, fitted centrally in the upper side of the substantiallyrectangular movable dead-beat helix 12. The rectangular movable helix 12comprises closely-bunched coils of wire and loosely encircles the core 8lengthwise thereof, so as to be free to turn around the core and in thespaces between the core andthe opposite poles of the permanent magnet,the pivotal support of the helix on top of the core providing for thedelicate balancing thereof, so that the same will readily respond to theslightest fluctuation in the strength of the current passing through thewire of the helix.

The loose pivotally-suspended helix has fixedly secured on the upperside thereof a bar-magnet 13,disposed longitudinally of said upper sideof the helix, with the ends thereof normally disposed in a line with theopposite poles of the magnet 6, the adjacent poles of the magnets 6 and13 being of different polarity, whereby the attraction of the unlikepoles of the two magnets will provide for maintaining the dead-beathelix in a proper normalpositionfor holding the pointer 14 at the zeropoint on the indicating scale. The pointer 14 is secured fast on top ofthe upper side of the helix 12, so as to move therewith, and at itsouter end the pointer is provided with an indicating-finger 15, workingover the top edge of the scale-plate and in front of thedegreegraduations thereon, so that the movement of the pointer willcarry the finger thereof over the scale to indicate the correcttemperature of the particular place or places in connection with whichthe instrument may happen to be employed.

In connection with the movable dead-beat helix 12 is employed aWheatstone bridge 16, suitably arranged within the box or case 1 at anyconvenient point, and the said bridge 16 is of an ordinaryconstruction,comprising four resistance-coils, three of which are madeof material whose resistance changes very little with Variation oftemperature. These three resistances, shown in a diamond group, areembedded in material (not shown) which is a bad conductor of heat. Thebridge has opposite end terminals 17, and the opposite side terminals18, intermediate of the said end terminals 17, and the fourth of theresistancecoils of the lVheatstone bridge 16, designated by the numeral19, forms the thermostatic coil of the instrument and is arranged at apoint remote from the other three resistances of the bridge andindicating mechanism mounted within the ease or box 1. The saidthermostatic coil 19 is preferably supported 011 an upright core 20within a tight casing 21, which serves to exclude moisture,dampness,orother foreign influences which would affect the coil 19 within thecasing, and the said casing carrying the coil 19 is placed in anyconvenient position within the room or other place where the temperatureis to be taken.

The thermostatic coil 19 of the instrument has its terminals connectedwith wire connections at 17, leading, respectively, to one end and sideterminal of the bridge 16, so as to complete the usual circuitconnections of the bridge, and in the present invention the opposit-eend terminals 17 of the bridge have respectively connected therewith thebatterywires 6 cl, leading to a battery 22, preferably arranged withinthe case or box 1,0r to another suitable source of electrical energy.

One of the battery-wires, designated as (Z, includes in the circuitthereof an ordinary circuit-closer or push-button 23, which isconveniently suspended by the wire (I, so as to hang below the bottom ofthe case or box 1 within convenient reach of the operator whenever it isdesired for the instrument to indicate the temperature of the place orplaces where the thermostatic coil or coils of the bridge is located, aswill be readily understood by those skilled in the art, it being notedthat one instrument can be thrown into circuit by means of a switch withany number of thermostatic coils distributed at different places.

One of the side terminals of the bridge 16 has connected thereto oneterminal of a circuit-wire c,- the other terminal of which is connectedwith the supporting-screw 9 of the core 8, which is in metallicconnection with the said screw. The current which passes through thecircuit-wire (2 also passes through the core 8, the pivot-pin 10, andthe bearing cup or socket 11, which bearing cup or socket 11 hasconnected therewith one of the wire terminals f of the helix 12, theother wire terminal g of which helix has a wire connection it with aheavier circuit-wire i, which connects with the side terminal 18 of theWheatstone bridge opposite the terminal with which the circuit-wire econnects.

Under conditions during which, in graduation when the four resistancesor arms of the lVheatstone bridge are balanced, the current from theminus or negative pole of the battery passes over the wire d to thecircuitcloser or push-button 23 and thence to the lower end terminal 17of the WVheatstone bridge. From this point the current then passesthrough the four resistances of the bridge to the upper end terminal 17thereof and thence through the battery-wire c to the positive terminalof the battery. The conditions which balance the bridge are that theexposed resistance or arm shall be at some constant temperature, zero orbelow or abor e zero, depending on the range of temperature theinstrument may be constructed for,while the three unexposed resistancesor arms, whose resistance varies but little with variation oftemperature and which are embedded in a bad conductor of heat, are atthe average temperature of the place where the indicatin g instrument isto be used. As stated, this would be the course of the current when thebridge is balanced under the above conditions, but the exposedresistance-coil 19 of the bridge located at a point remote from theindicating instrument, when exposed to any temperature above or belowthe temperature at which the instrument was originally balanced, theresistance ofsaid coil is varied and becomes unequal to the resistancesof the other three coils of the bridge, thereby unbalancing the bridgeand causing a portion of the current to pass through theindicator-circuit e h z'. The indicator-circuit c ht includes theloosely=suspended helix, and in passing through the convolutions orcoils of the helix the helix becomes as a magnet, following all the lawsof a magnetized body, and the permanent magnet 6 will cause the helix toturn, thereby causing the finger of the pointer to move over the scaleand indicate the precise degree of temperature of the place where thethermostatic coil 19 is located. It will of course be understood thatthe instrument is put in operation by closing the circuit manually atthe circuit-closer or push-button 23, which is of an ordinaryconstruction. When the helix is relieved of the current, the same isreturned to a proper normal position by the magnet 13, the poles ofwhich are attracted by the adjacent unlike poles of the permanent magnet6.

From the foregoing it is thought that the construction, operation, andmany advantages of the herein-described electric thermometer will bereadily apparent to those skilled in the art without furtherdescription, and it will be understood that various changes in the form,proportion, and the minor details of construction may be resorted towithout departing from the principle or sacrificing any of theadvantages of this invention.

Having thus described the invention, what is claimed and desired to besecured by Letters Patent, is

1. In an electric thermometer, a IVheatstone bridge included in abattery-circuit and having one of its resistancecoils isolated at aremote point to form a thermostatic coil, a suitably-arranged scale, astationary permanent magnet having oppositely-arranged poles, adead-beat helix or coilpivotally suspended from a fixed point of balancebetween the poles of the permanent magnet and having circuit-wireconnections with the bridge, and a pointer moving over the scale andfitted directly to the dead-beat helix or coil, substantially asdescribed.

2. In an electric thermometer, a VVheatstone bridge included in abattery-circuitandhaving one of its resistance-coils isolated at aremote point to form a thermostatic coil, a suitably-arranged scale, astationary permanent magnet having oppositely-arranged poles, astationary metallic core supported between the poles of the permanentmagnet, a pivotally-suspended helix loosely encircling the core betweenthe poles of the permanent magnet and carrying a pointer, and circuitWire connections between said helix and the Wheatstone bridge,substantially as set forth.

In an electric thermometer, a heatstone bridge included in abattery-circuit and having one of its resistance-coils isolated at aremote point to form a thermostatic coil,

' a suitably-arranged scale, a stationary permanent magnet havingoppositely-arranged poles, as tationary metallic core supported betweenthe poles of the permanent magnet, a pivotally-suspended helix looselyencircling the core and carrying a pointer, circuit-wire connectionsbetween the helix and the bridge, and a readjusting-bar magnet fitted onthe helix between the" opposite poles of the permanent magnet,substantially as set forth.

4. In an electric thermometer, a case or box provided with an enlargedupper portion having a glass-covered open front side, a curvedscale-plate fitted Within the front side of the upper portion of thecase, a Wheatstone bridge arranged in the case and in cluded in abattery-circuit, one of the resistance-coils of the bridge beingisolated at a remote point to form a thermostatic coil, and a 1nagnetically-influenced movable body having circuit-wire connections withthe bridge and carrying a pointer provided with a finger moving over thetop edge of the scale-plate, substantially as set forth. 5. In anelectric thermometer, a Wheatstone bridge included in a battery-circuitand having one of its resistance-coils isolated at a remote point toform a thermostatic coil, I

a suitably-arranged scale, a stationary permanent magnet havingoppositely-arranged poles, a stationary metallic core supported betweenthe poles of the magnet and provided at its upper end with a shortpivot-pin, a movable dead-beat helix loosely encircling the stationarycore between the poles of the permanent magnet and carrying centrally atits upper side a bearing cup or socket loosely turning on said shortpivot-pin, circuit-wire connections between the two terminals of thehelix and two opposite terminals'of the bridge, a readjusting-bar magnetfitted on the upper side of the helix, and a pointer attached tothehelix, substantially as set forth.

In testimony that I claim the foregoing as my own I have hereto affixedmy signature in the presence of two witnesses.

MICHAEL ALEXANDER AGELASTO. Witnesses HENRY B. CONSTABLE, GEO. W.NEVILLE.

